import sys
from PyQt5.QtWidgets import QWidget,QDesktopWidget,QApplication

class Example(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.resize(250,150)
        self.center()

        self.setWindowTitle('Center')
        self.show()

    def center(self):
        qr=self.frameGeometry()
        cp=QDesktopWidget().availableGeometry().center()
        qr.moveCenter(cp)
        self.move(qr.topLeft())

if __name__=='__main__':
    app=QApplication(sys.argv)
    ex=Example()
    sys.exit(app.exec_())
